1. Field of the Invention
The present invention relates to a flexible printed circuit which is used for an optical instrument such as a camera, VTR integrated with a camera, an electronic still camera and the like, and more particularly to a flexible printed circuit including a positioning hole which is used for positioning the flexible printed circuit at the time of a continuity test.
2. Description of the Related Art
The conventional flexible printed circuit is mainly composed of a base member made of soft material, a wiring pattern made of copper (Cu), etc., and a cover layer. The wiring pattern is printed on the front surface of the base member. After this, the cover layer is adhered to the base member. Further, a reinforcing plate is adhered to the back surface of the base if necessary.
A plurality of test terminals are included in the wiring pattern in addition to a terminal which is to be connected to an IC, etc.. The test terminal is used for a continuity test which is to be carried out before the flexible printed circuit is delivered. Moreover, a plurality of openings are provided in the cover layer so as to expose the test terminals.
At the time of the continuity test, the flexible printed circuit is to be positioned on a stage of the inspecting machine in order that an inspection contacts of the inspecting machine is in contact with the test terminals through the openings of the cover layer. Therefore, the flexible printed circuit has a positioning hole, and a positioning piece of the inspection machine is inserted in the positioning hole in order to position the flexible printed circuit correctly on the stage.
There are two kind of inspection machines which is used for the continuity test, that is, one is the machine which moves one inspection contact towards each of the test terminals with the positioning piece being its reference, and the other is the machine which is provided with the same number of inspection contacts as the test terminals so that all the inspection contacts are made contact with the test terminal at once.
The positioning hole is formed in the flexible printed circuit at the time of punching the external shape of the flexible printed circuit after the cover layer is adhered to the base member.
However, the cover layer is sometimes adhered to the base member in such a manner that the openings does not perfectly correspond to each of the test terminals, and the positioning hole is sometimes formed in a wrong position at the time of punching the external shape. In the case that the flexible printed circuit is made in such a state, the flexible printed circuit is positioned on the basis of the wrongly formed positioning hole. Therefore, there is problem in that the inspection contacts imperfectly come into contact with the test terminals. As a result, the continuity test can not be well carried out.